When I was in graduate school many happy years ago, I took a linguistics course in which the instructor warned us never to get into an argument with anyone about grammar. We would only lose. So of course I commenced a career as an English teacher and an editor; in the pursuit of my duties I had perforce to argue with people about grammar. It's just a way I have of going about things.
In that linguistics class I learned the age at which one attains linguistic competence. It's three. Five at the outside. This is well before getting into elementary school you'll notice, well before getting the first instruction into grammar. In my bright-eyed way, when I first started teaching, I mistakenly thought that I was bringing my students good news, the news that far from being bad at grammar, which is what everyone in the US is taught to think of themselves, they had mastered the intricacies of the language they were born with before they even got to first grade.
No one wanted to hear that. Convinced that they didn't know the rules and oddly desirous of learning them, once and for all, they wanted only to be instructed in what they had been taught to call “proper” grammar. A large part of it was fear, of course, a fear instilled in them from third grade that if they made any mistakes people would make fun of them. But another part of it, allied to fear, was a desire for control. If they could master the rules, they could eventually become the mockers instead of the mocked.
How did this situation come about? In what was once called “grammar school,” you are told that you don't know your grammar. You do know the grammar, however, and you have known it for years. What you don't know in third grade is the vocabulary. Your knowledge of grammar is like your knowledge of breathing; you don't have to think about it or know anything about physiology to do it. Simply learning the words for your knowledge should fine. But what you get in school, at least in the US, does not match very well with your knowledge. It matches Latin, more or less, but it matches only occasionally and capriciously and unpredictably with what you already know to be true about English.
But you're a kid, your knowledge is innate and inarticulable, and an adult in authority is telling you things that you have neither the skills nor the conscious knowledge to defend yourself against. Not to mention. So you learn words for things—nouns, verbs, modifiers, syntax—but instead of descriptions that match your knowledge, you learn a lot of rules, the worst of which are simply made up, the best of which apply to a vastly different language than your own. You learn very clearly that you don't know something that you know perfectly well and have known for many years. You can probably easily recall the definition of “noun,” right? The name of a person, place, or thing. Fine as far as it goes, which isn't nearly far enough. What you know as a native English speaker is that whatever has a “the” in front of it, and maybe a “big” or a “blue,” in front of it, too, is a noun. Not every word is going to work equally well with a “the” in front of it, but as a native speaker, you know that as well. Your knowledge is really pretty sophisticated.
Eventually, something else happens to you in school—writing instruction. It was bad enough to be taught all that stuff back in third grade that matched up very badly if at all with your innate knowledge of your native language. Now you have to confront the vagaries of writing, often without any instruction about how writing differs from speaking. Speaking is natural for humans. Writing is not. And since writing instruction more often than not pitches the same faulty rules at you that had so ruined your confidence in third grade, even if your instructor tells you that speaking and writing are different, gently explicating the differences for you, you end up only learning one more thing in life in which you are bound to fail.
Great.
So now what?
Well, for the grammar police, I have a request—resign.
For the writers, I have an observation—you will make mistakes. But even those mistakes that aren't simply owing to fumble fingers are not signs of encroaching social and moral decay, as certain of your colleagues will tell you; they are not evidence that you don't know grammar, and they rarely impede communication. Any reader, reading any text, will supply corrections to errors, consciously or unconsciously. If you can spot an error, then you have understood what was intended. So much for “communication” being the reason for being so concerned about infractions. Communication has happened anyway, in spite of the error.
It shouldn't need mentioning, but an error free text is not necessarily a well-written text. Attention to errors will not take you very far, stylistically. Your prose might be clean, but if it's boring and awkward, you've failed. And if there's one thing you learned in school, it was that you are a failure, right? Well, you're not, but who couldn't use a spot of improvement now and again, just for giggles? So here's the most important advice for anyone who writes: read.
Read widely and often. Read outside your areas of interest. Read not just for content but for style. You have learned how to read for content. You've got that, already. But knowing your topic doesn't take you very far when you're writing. When you're writing, you need something besides knowledge of your topic. You need style. Style is, after all, what makes the content what it is. So when you read something, notice the sentence structures, vocabulary, punctuation, paragraphing. Whatever the topic, the act of writing is about making, and to make something, you have to know about your materials and about your tools. So there you have it. And here's a word of comfort: even if you don't have an extensive training in rhetoric and syntax, if you read a lot, and if you read widely, you will inevitably acquire a sense of what works and what doesn't. You may not know the vocabulary, but in common with your third grade self, your knowledge is still knowledge.